THE VASCULAR SYSTEM 



337 



mon origin of the supra- and infra-orbital and mandibular 

 arteries has become lost and their source of supply has become 

 transferred to the dorsal stump of II. The artery thus formed 

 penetrates the mass of cells destined to become the stapes and 

 forms the foramen characteristic of this bone in the higher 



FIG. 94. (h)-(l), Continuation of the series given in Fig. 93. (m), 

 Ultimate condition in Man, for comparison with (1). [All figures after 

 TANDLER.] 



xy, the artery formed by the union of x, and y, in the previous figure; cc, 

 common carotid artery; ce, external carotid artery; ci, internal carotid artery; st, 

 stapedial artery; n, anastomosing branch between the external carotid and mandib- 

 ular arteries. The other abbreviations are given under FIG. 93 or are explained 

 in the text. 



Mammalia. In the monotremes, where this action does not 

 take place, the bone is columnar, and without a foramen. From 

 now on the artery formed by the dorsal stump of arch II, the 

 anastomosing branch (xy), and a bit of the dorsal stump of 

 arch I, becomes called the stapedialis (st), through its relation- 



